If the 800-degree heat or crushing atmospheric pressure doesn't get you, you might want to watch out for spewing plumes of sulfur dioxide and liquid lava flows on your next visit to Venus. We've long known that our neighboring planet has lots of volcanoes, but no one is sure if any of them are currently active. It's impossible to see through Venus' dense CO2 atmosphere, but the European Space Agency's Venus Express orbiter has found evidence of drastic, sudden chemical changes at high altitudes. An active volcano might be the culprit.

Because of the immense atmospheric pressure on Venus (more than 90 times higher than sea level Earth air pressure), it's unlikely that a volcano there would erupt explosively. However, it could emit sulfur dioxide into the upper atmosphere as liquid lava flows down the volcano's flank. The Venus Express looks at the sun through Venus' atmosphere, then uses spectroscopy to identify the chemicals there. It observed a more than 60 percent drop in sulfur dioxide levels over just a few days, strong evidence of an intermittent source of that gas. ESA scientists want to use more spectroscopy to spot a tell-tale gas plume, or infrared sensors to find volcanic hot spots. Photo by NASA.